1. Field of the Invention
The present invention relates to a conveyor apparatus for plate-form articles such as lead frames, etc.
2. Prior Art
Japanese Patent Application Laid-Open (Kokai) No. 62-235742 discloses one of the conventional apparatuses for conveying plate-form articles such as frames, etc.
The apparatus disclosed in this publication includes: a common main conveyor line which is installed in front of a multiple number of identical working devices; a working conveyor line installed on both sides of the working devices; and a sub-conveyor means that consists of a belt conveyor which is installed at right angles relative to and between the main conveyor and working conveyor lines.
In this apparatus, a lead frame conveyed by the main conveyor line is received by the sub-conveyor means installed on a supply side and then conveyed in a direction perpendicular to the main conveyor line. Thus, the lead frame is transferred to the working conveyor line on the supply side. Then, the lead frame is sent to the working devices by the working conveyor line and worked by the working devices. When the working is completed on the lead frame, the lead frame is conveyed to the working conveyor line on a discharge side and then received by the sub-conveyor means on the discharge side. The lead frame is thereafter transferred back to the main conveyor line by the sub-conveyor means.
Since the sub-conveyor means in the apparatus described above consists of a belt conveyor, it involves problems as described below:
Some lead frames have "islands" which are depressed areas in which pellets are installed. The "islands" are at the central area of the lead frame and formed at equal intervals in its length-wise direction.
When conveyed by the main and working conveyor lines, the lead frame is supported at both ends in the length-wise direction; thus, no problems would occur in the conveyance. However, on the sub-conveyor means, the lead frame is positioned so that its longer sides are positioned at right angles relative to the conveying direction of the sub-conveyor means. As a result, the island tends to be caught by belts, which are provided in a plurality number so as to meet the lead frames of different lengths. As a result, a smooth conveyance is occasionally impeded.
Furthermore, the island is supported at both ends by narrow linear portions of the lead frame; accordingly, an external load is applied on the island by the weight of the lead frame when the island is directly on the belts. This would result in a wire deformation if a wire-bonding has been completed on a lead frame.